首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1588篇
  免费   102篇
  国内免费   149篇
林业   113篇
农学   64篇
基础科学   32篇
  130篇
综合类   783篇
农作物   116篇
水产渔业   156篇
畜牧兽医   198篇
园艺   202篇
植物保护   45篇
  2024年   11篇
  2023年   29篇
  2022年   62篇
  2021年   81篇
  2020年   70篇
  2019年   55篇
  2018年   49篇
  2017年   76篇
  2016年   48篇
  2015年   81篇
  2014年   100篇
  2013年   124篇
  2012年   128篇
  2011年   127篇
  2010年   150篇
  2009年   125篇
  2008年   107篇
  2007年   129篇
  2006年   69篇
  2005年   60篇
  2004年   32篇
  2003年   10篇
  2002年   27篇
  2001年   26篇
  2000年   30篇
  1999年   8篇
  1998年   4篇
  1997年   3篇
  1994年   2篇
  1993年   2篇
  1992年   1篇
  1990年   6篇
  1989年   1篇
  1969年   1篇
  1962年   1篇
  1955年   3篇
  1931年   1篇
排序方式: 共有1839条查询结果,搜索用时 15 毫秒
1.
山植酱酸甜可口,营养丰富,色释诱人,是佐餐佳品。且山楂来源广,价格较低。适合家庭制作,现将生产过程介绍如下:  相似文献   
2.
AIM: To examine the expression of human endostatin in E.coli, produce its fusion protein antibody and observe its biological activity. METHODS: Endostatin gene was amplified by polymerase chain reaction,recombined with plasmid vector pGEX-2T and induced expression with IPTG.The protein activity was tested by endothelial cell proliferation inhibitory assay.Inclusion body crudely purified was used to generate polyclonal antibody to detect its expression at mouse's liver and kidney etc. RESULTS: The protein expressed was 20kD after digestion by thrombin,it appeared the anti-angiogenesis activity and Western blotting indicated the expression of endostatin in liver and kidney of mouse. CONCLUSION: The successful expression of human endostatin and the preparation of polycolonal antibody indicated its potential application in anti-angiogenesis therapy and diagnosis tumors.  相似文献   
3.
五种鬼伞过氧化物酶和酯酶的同工酶研究   总被引:2,自引:0,他引:2  
应用垂直板聚丙烯酰胺凝胶电泳对五种野生鬼伞 (Coprinus)真菌进行了过氧化物酶 (POD)和酯酶(EST)的同工酶分析 ,结果表明 :五种鬼伞的POD和EST同工酶酶谱比较稳定清晰 ,且分别有一条共同的酶带 ,可能是鬼伞属的POD和EST同工酶特征酶带 ;POD和EST同工酶酶谱均表明 ,家园鬼伞 (C .domesticus)和瓦鳞鬼伞 (C .clavatus)间有较近的亲缘关系 ;不同种鬼伞的POD和EST同工酶之间既有共同的特征 ,又各自有本物种的特有特征 ,POD和EST同工酶酶谱可以作为鬼伞属种类鉴定、亲缘关系比较的重要依据。  相似文献   
4.
AIM: To determine the role of Kv1.2, Kv1.5, Kv2.1 in the hypoxia pulmonary vasoconstriction (HPV). METHODS: Male Wistar rats were divided into two groups: normoxic group and hypoxic group. The single smooth muscle cell was obtained from pulmonary artery of Wistar rats with acute enzymatic digestion method. The conventional whole-cell patch clamp technique was used to record the resting membrane potential (Em) and the potassium currents of voltage-gated potassium channel (IKv) in rat pulmonary arterial smooth muscle cells (PASMC). Intracellular application of Kv1.2/Kv1.5/Kv2.1 antibodies (1∶125) was conducted through the whole-cell patch clamp system. RESULTS: ① Em of PASMC was depolarized after 24 h hypoxia compared with that of control cells . IKv of PASMC was decreased after 24 h hypoxia, . ② The mixture of Kv1.2/Kv1.5/Kv2.1 antibodies depolarized Em and inhibited IKv in PASMC from normoxic rat, whereas the mixture of Kir2.1/Kir2.3/Kir4.1 antibodies had no effects on them. ③ The mixture of Kv1.2/Kv1.5/Kv2.1 antibodies and the mixture of Kir2.1/Kir2.3/Kir4.1 antibodies had no effects on IKv and Em from rats hypoxic for 24 h. CONCLUSION: Kv1.2, Kv1.5, Kv2.1 might be oxygen sensitive potassium channels which mediated HPV.  相似文献   
5.
Endothelial progenitor cell (EPC) is a kind of directional cell that is able to differentiate to endothelial cell. The role of EPC is associated not only with vasculogenesis during embryonic development but also with physiological organ maintenance and angiogenesis during postnatal and adult period. There is a good clinical therapeutic prospective use for EPC in the treatment of ischemia diseases and inhibition of tumor angiogenesis.  相似文献   
6.
Development of new semen cryopreservation techniques improving sperm survival and ensuring availability of viable spermatozoa for a prolonged time‐period after AI is promising tools to reduce sensitivity of timing of AI and enhance overall fertility. The SpermVital® technology utilizes immobilization of bull spermatozoa in a solid network of alginate gel prior to freezing, which will provide a gradual release of spermatozoa after AI. The objective of this study was to compare post‐thaw sperm quality and in vitro sperm survival over time of Norwegian Red bull semen processed by the SpermVital® (SV) technology, the first commercialized production line of SpermVital® (C) and by conventional procedure applying Biladyl® extender (B). Post‐thaw sperm motility was not significantly different between SV, C and B semen (p > .05). However, sperm viability and acrosome intactness were higher for SV than C and B semen (p < .05). Small differences in DNA quality were observed (p < .05). Sperm viability after storage in uterus ex vivo was higher for SV than for C semen (p < .05). Furthermore, sperm survival in vitro over time at physiological temperature was significantly higher for SV semen than C semen as well as B semen during the incubation period of 48 hr (p < .05). In conclusion, the SpermVital® technology is improved and is more efficient in conserving post‐thaw sperm quality and results in higher sperm viability over time in vitro for SV than for C and B semen.  相似文献   
7.
以6 个菱品种为试材,对花器形态特征、群体花期及单花开花动态、开花时间、柱头可授性、花粉活力、杂交指数 及传粉形式等进行观察测定。结果表明:菱花单生,两性,单花花期15 h,群体花期在5~10 月,盛花期在7~8 月;不同 品种在一天中的开花高峰期存在差异;柱头可授期主要在萼片开裂后2 h 内,结实率在50% 以上;花粉在自然授粉条件下活 力可保持7.5 h;以自花授粉为主,同时存在一定程度的无融合生殖和少量异花授粉。  相似文献   
8.
研究心房钠尿肽基因敲除小鼠(ANP-/-小鼠)的生物学及病理学特性。ANP-/-小鼠与C57BL/6小鼠饲养于SPF级环境中,观察小鼠的繁育状况及其生物学特性,选取合适时间处死小鼠,通过HE染色观察脏器形态及组织结构。ANP-/-小鼠的繁殖周期比C57BL/6长,产仔率较低;ANP-/-小鼠肝脏、肺脏、脾脏较C57BL/6小鼠的有明显炎症反应,但是C57BL/6小鼠未见明显的病理改变。提示ANP基因的缺失可能与炎症发生有关。说明ANP-/-小鼠繁殖较慢、产仔率低,且正常繁殖的普通小鼠不会引起器官的病理学改变。但作为一种在心血管、代谢疾病上的动物模型,并与炎症甚至肿瘤有可能的未知联系的转基因动物,其很有研究和探索价值。  相似文献   
9.
针对天门冬[Asparagus cochinchinensis(Lour.)Merr.]成熟叶片富含多糖、多酚、蛋白质及其他次生代谢物质的特点,采用改良CTAB法对其基因组总DNA进行提取,并对DNA进行质量检测。结果表明,改良CTAB法可从天门冬成熟叶片中获得纯度高、完整性好的总DNA,其OD260 nm/OD280 nm为1.86,OD260 nm/OD230 nm为2.36,浓度为390μg/mL,产率达11.7μg/g,多糖、多酚和RNA杂质被去除干净,无降解现象,说明该方法提取的天门冬基因组总DNA质量较高。  相似文献   
10.
家兔失血性休克实验是《医学机能学》实验中的一个重要组成部分,在日常教学过程中,传统经典实验只观察血压的变化,针对这一问题,我院引进BI-2000图像分析系统,并在2014级临床医学教改班家兔失血性休克实验中应用,使学生对于休克发生、进展的机制有了更深刻的理解,对休克各期微循环血液灌流的变化特点有了更直观的认识。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号